Abstract

Photoluminescent properties of the Eu³⁺ ion as a probe are studied in γ-, η-, θ-, and α-Al₂O₃:Eu³⁺ polymorphs with an europium concentration of 0.05 wt.%. The photoluminescence (PL) spectra of Eu³⁺ ions are analyzed in the ⁵D₀ → ⁷F_J (J = 0-4) transition region along with the asymmetry ratio, decay kinetics, and PL excitation spectra. It is found that Eu³⁺ ions incorporate into the Al₂O₃ lattice and occupy the site with the C_3v local symmetry. The biexponential nature of the Eu³⁺ PL decay kinetics in γ-, η-, θ-, and Al₂O₃:Eu³⁺ polymorphs is shown to be due to the occurrence of Eu³⁺ ions both in the bulk and at subsurface sites. For α-Al₂O₃:Eu³⁺ the concentration of surface centers is minimum and the PL decay kinetics is described only by one exponent. Based on the comprehensive analysis of the obtained results on PL of single-phase Al₂O₃ powders, the characteristic features are revealed, such as PL intensity, electronic structure of ⁵D₀ → ⁷F_J transitions, asymmetry ratio, position of the O^2– → Eu³⁺ charge transfer band, and ⁵D₀ lifetimes. These characteristics allow the use of Eu³⁺ ions as structure-sensitive probes to study the local structure of Al₂O₃ and to identify its phase composition during structural transformations.

中文翻译：

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Eu3+ 在不同 γ-、η-、θ- 和 α-Al2O3 多晶型物中的光致发光性质

摘要

在铕浓度为0.05 wt.%的γ-、η-、θ-和α-Al ₂ O ₃ :Eu ³⁺多晶型物中研究了Eu 3+ 离子作为探针的^光致发光性质。分析了Eu ^3+离子在5 D ₀  →  ⁷ F _J ( J = 0-4) 过渡区的光致发光 (PL) 光谱 以及不对称率、衰变动力学和 PL 激发光谱。发现Eu ³⁺离子结合到Al ₂ O _{3晶格中并占据具有}C _{3 v}局域对称性的位置。γ-、η-、θ- 和 Al ₂ O ₃ : Eu ^{3+多晶型物中 Eu 3+} PL 衰变动力学的双指数性质被证明是由于 Eu ³⁺离子在本体中和在地下站点。对于α-Al ₂ O ₃ :Eu ^{3+ ，}表面中心的浓度最小并且PL衰变动力学仅由一个指数描述。_{通过对单相Al 2} O ₃粉末PL结果的综合分析，揭示了PL强度、⁵ D ₀  →  ⁷ F _J跃迁的电子结构、不对称率、位置等特征。 O ^2–  → Eu ³⁺电荷转移带和⁵ D ₀寿命。这些特性允许使用Eu ³⁺离子作为结构敏感探针来研究Al ₂ O ₃的局部结构并识别其结构转变过程中的相组成。